The present invention relates to a novel apparatus for measuring strain in a rotating shaft and, more particularly, to a new and novel system for measuring strain experienced over a precise length of a rotating shaft.
Thus, a primary object of the present invention is to provide improved apparatus for measuring strain in a vibrating and/or rotating shaft.
A further important object of the present invention is to provide a strain meter which can be easily clamped onto shafts of different sizes and which is reliable and easily calibrated by determining shaft radius and effective operating radius of the linear variable differential transformer.
The present invention is summarized in that there is provided apparatus for measuring strain in a vibrating and/or rotating shaft. First and second spaced blocks are clamped to the shaft and rotate therewith. A linear variable differential transformer (LVDT) is affixed to the first block and a displacement arm is affixed to the second block. A LVDT core is attached to the displacement arm and disposed to be movable without contact within and through the LVDT. A flexible cable extends from the displacement arm to the LVDT and maintains the LVDT core at an adjustable radial position relative to the axis of rotation of the shaft. A vertical stabilizing bar is affixed to each block and includes a relief cutout section adjacent to the second block to accommodate the shaft flexure about its neutral axis. Oscillation dampers connect the displacement arm to the stabilizing bar. Shaft strain between the blocks is sensed at the LVDT and information signals indicative of the strain are telemetered off the shaft.